JP4537061B2 - Method and apparatus for mechanically masking a workpiece - Google Patents

Description

(Cross-reference of related applications)
The present application is entitled “METHOD AND APPARATUS FOR OPTICALLY DEFINING AN EXPOSURE EXCLUSION REGION ON A PHOTOSENSITIVE WORLD PIECE WORKING” filed on the same day as the present application. And a pending US patent application Ser. No. 09 / 923,755 entitled “METHOD AND APPARATUS FOR MASKING A WORKPIECE WITH INK”.

  The present invention relates to lithographic exposure and patterning of workpieces. In particular, the present invention relates to a mechanical method and apparatus for preventing exposure of selected areas on a workpiece by selectively masking the workpiece.

  Lithographic techniques are used in the manufacture of micro devices such as integrated circuit (IC), flat panel displays, microelectromechanical systems (MEMS), bump IC wiring formation for flip chip wiring technology, and the like. The lithography process uses a photosensitive workpiece (wafer) and selectively exposes the workpiece with radiation (such as ultraviolet light). The photosensitivity of the workpiece is obtained by coating or applying a layer of a photosensitive material called photoresist on the surface of the workpiece. The photoresist may be either “positive type” in which the exposed resist is removed by development, or “negative type” in which the unexposed resist is removed by development.

  In general, a lithographic process involves coating a workpiece with a photoresist, exposing the photoresist through a mask image to form a latent image in the photoresist, and developing the photoresist to produce a three-dimensional image. , Forming a corresponding three-dimensional pattern on the workpiece, and removing excess photoresist. These steps are repeated as many times as necessary to form a predetermined device structure on the workpiece.

  In lithography using negative photoresist, selected areas of the workpiece that are outside the individual exposure fields are preferably not fully exposed so that the resist in the selected areas is removed during development.

  Bump wiring lithography is one example, and bump wiring lithography uses conductive (eg, gold, solder alloy, or other suitable metal) bumps that are used to connect circuit wiring on a circuit board to a workpiece (wafer). ) Forming on. Bump lithography includes an electrochemical plating process for forming conductive bumps. In this step, most of the edge of the wafer needs to be in contact with the electrode. Further, the resist layer used for bump lithography is relatively thick (for example, 50 μm) as compared to so-called front-end lithography. In bump lithography, the entire edge of the wafer must not be substantially covered with photoresist in order to ensure uniform electrical contact.

  When one-to-one contact photolithography or near-contact photolithography is performed, the entire wafer is exposed at the same time, and a desired exclusion region is incorporated into the reticle so that the end portion is not exposed. 200 mm or 300 mm wafer contact lithography or near contact lithography is limited by defects, large and expensive masks, and mask contamination. Although step-and-repeat lithography can eliminate these drawbacks, the exposure often overlaps the wafer edge when it is not desirable to expose the wafer edge or its vicinity. However, in step-and-repeat photolithography, the step pattern depends on the pattern size and the step size, so that it is impossible to define an exclusion area on the reticle. Accordingly, there is a need for a method and apparatus for defining an exposure exclusion region on a workpiece in a photolithography process. The present invention provides such a method and apparatus.

  The present invention relates to lithographic exposure and patterning of workpieces using reduced lithography or 1X step-and-repeat lithography. In particular, the present invention relates to a mechanical method and apparatus for preventing selected areas of a workpiece from being exposed by selectively masking the workpiece.

  A first aspect of the present invention is a method for forming one or more exposure exclusion regions on a photosensitive workpiece that is exposed by a drawing apparatus capable of printing a micro shape on the workpiece. The method includes selecting one or more unexposed areas of the photosensitive workpiece and masking one or more selected macro areas of the workpiece. This is accomplished by placing a mask that is opaque to the wavelength of radiation that activates the photosensitive workpiece in proximity to (ie, on or near) the surface of the workpiece. After the workpiece is exposed, the mask is removed and the workpiece is processed. In the case of using a negative type photoresist, a portion corresponding to an exposure exclusion area of the photoresist is removed during development, and the surface of the workpiece is exposed.

  A second aspect of the present invention is an apparatus for forming one or more exposure exclusion regions on a photosensitive workpiece. The apparatus includes a mask that is opaque to the wavelength of radiation that activates the photosensitive workpiece. A mask is placed proximate to the photosensitive workpiece so as to cover a selected macro area of the workpiece. In a preferred embodiment, the mask is a ring having a size that covers the (annular) region adjacent to the end of the workpiece. The apparatus may further include a mask handling apparatus configured to transport the mask to the workpiece.

  The present invention relates to lithographic exposure and patterning of workpieces. In particular, the present invention relates to a mechanical method and apparatus for preventing selected areas of a workpiece from being exposed by selectively masking the workpiece.

  In the present invention, the term “mask” refers to the mechanical mask apparatus of the present invention and a workpiece that is located above the projection lens and performs front-end lithography exposure (for example, exposure that defines the limit level of a semiconductor device). Used to distinguish from a reticle (also called a “mask”) that contains a small pattern drawn on a piece.

  As shown in FIG. 1, a standard lithography tool 10 sequentially exposes an illumination system 12, a reticle R supported by a reticle stage RS, a projection lens 14, and an image of the reticle R along an axis A0. A workpiece stage 16 that movably supports 30 is included. Workpiece 30 includes an upper surface 32 and an end 34. The workpiece stage 16 is designed to movably support the workpiece 30 under the projection lens 14. The workpiece 30 is fixed to the workpiece stage by a vacuum before starting the operation of the workpiece stage.

  The workpiece 30 is moved under the projection lens by the workpiece stage 16 so that a plurality of exposure fields 36 (FIG. 2) can be formed (exposed) on the workpiece by lithography. In one embodiment of the present invention, the upper surface 32 of the workpiece 30 is photosensitive and includes a negative photoresist layer 40 that typically has a thin protective coating (not shown). An example of a suitable negative photoresist for use in the present invention is LISTON (registered trademark) manufactured by DuPont. The Liston includes a thin MYLAR® coating that is transparent to the exposure radiation wavelength.

  The lithography tool 10 includes a main controller 44 that controls the operation of the lithography tool and is operatively connected to the workpiece stage 16 to control the initial alignment and transfer of the workpiece to the workpiece stage 16. Further, in conjunction with the lithography exposure process for forming the exposure field 36, the main controller 44 optionally controls a mechanical mask method (details will be described later) for forming one or more exposure exclusion regions on the workpiece. And adjust.

  As shown in FIG. 3, a mask handling device 60 designed to operate (engage, move, disengage) a workpiece mask 70 used to perform the exposure exclusion method of the present invention comprises a workpiece stage. 16 is operatively connected. In the present invention, the exposure exclusion region defined by the mask 70 is not a micro (that is, an order of 10 μm or less) but a macro (that is, an order of 1 mm or more). Preferably, the mask is used in combination with a reticle and drawing apparatus (eg, tool 10) used primarily to print micro features on the workpiece. The present invention includes preventing selected macro areas on a workpiece from being exposed during lithographic printing.

  A workpiece mask (hereinafter referred to as “mask”) 70 is an opaque member, and at least a part thereof is located on or near the photosensitive surface 32 of the workpiece 30 (for example, on the photoresist layer 40). Here, “opaque” means that the mask does not substantially transmit light having a wavelength that activates the photosensitive surface 32 (eg, photoresist) of the workpiece 30. When using a listen or other suitable dry film photoresist for the negative photoresist layer 40, the mask 70 can be placed directly on the Mylar layer covering the resist.

  The mask 70 may be any opaque material and is preferably a lightweight plastic or metal. When the mask 70 is handled using the magnet handling device 60, the mask 70 is preferably a metal so that the mask 70 can be handled. When the mask 70 is handled using the vacuum handling device 60, a non-conductive material such as plastic or paper can be used.

  As shown in FIGS. 4 and 5, in a preferred embodiment, the mask 70 has a ring shape that includes a body 72 having a lower surface 73 and an upper surface 74. Ring mask 70 includes a lip 76 extending inwardly from body 72 at or near upper surface 74. In one embodiment, the width of the edge 76 is about 1-5 mm. In one embodiment, the edge 76 of the ring mask 70 has a thickness of about 5-15 mils and a radius of about 50-150 mm in all parts. The shape of the mask 70 depends on the size of the workpiece 30 and the shape of the desired exposure exclusion region to be formed. Preferably, the ring is in stock so that it can be used for different workpieces. In many applications, such as bump lithography, a standard size (eg, 100-300 mm) wafer is used as a workpiece so that only one or a few masks (eg, several types of ring masks with different radii and widths) are required. .

  As shown in FIG. 3, in one embodiment, the mask handling apparatus 60 includes a motor-driven platform 100 from which a beam 104 having a distal end 110 extends. The beam 104 can rise or fall on the platform 100 and rotate about the axis A1. An arm 120 is mounted on the end portion 110 and extends outward. Each arm 120 has a contact member 140 at its end designed to contact and selectively engage the mask 70. For example, the contact member 140 may be a vacuum pad that engages the mask 70 with sufficient vacuum to lift the mask. In another example, the contact member 140 may be an electromagnet that can be energized to engage and lift the mask 70. In yet another example, the contact member 140 may be a retractable clip that can engage the mask 70 and lift the mask 70. As such, contact member 140 may be any known device suitable for engaging and lifting mask 70. The arm 120 and contact member 140 constitute a mask lifting member 142 that is raised and lowered to accurately place the mask 70 on the workpiece and engage the mask to lift the mask off the workpiece.

  The mask handling device 60 preferably includes a mask handling control unit 200 connected to the table 100 and also connected to the main controller 44. The control unit 200 controls the engagement, accurate conveyance, and disengagement of the mask 70 when masking and removing the workpiece. The controller 200 may be independently programmable or controlled by the main controller 44 so that the photolithography exposure process is aligned with the workpiece masking.

As shown in FIGS. 5 and 6, it is constrained to the workpiece surface by two or more balls 202 attached to the lower surface 73 of the ring and pressed against a corresponding restraining member 204 disposed on the workpiece stage 16. In addition, the mask 70 is dynamically positioned with respect to the wafer chuck. The restraining member 204 preferably has a v-groove 206 sized to engage the ball 202. The restraining member 204 is designed to prevent the mask 70 from moving horizontally or rotating about the vertical axis when the mask 70 is placed in close proximity to the workpiece. Since the vertical movement is free, the ring mask can be in direct contact with the upper surface of the resist layer 40.
Method of Operation A method of forming the exposure exclusion region on the workpiece 30 will be described with reference to FIG. First, as shown in FIG. 3, the workpiece 30 is preferably placed on the workpiece stage 16 that has been moved from under the projection lens 14 to the workpiece mounting position. Next, one or more areas where the surface of the photosensitive workpiece is not exposed (ie, an exposure exclusion area) is determined, and a mask 70 corresponding to the area is selected.

  When the first workpiece 30 is correctly placed on the workpiece stage 16, the mask handling device 60 is activated and an instruction is given via the controller 200 to transport the appropriate mask 70 toward the workpiece. Usually, a mask in a mask library (not shown) is engaged with the mask lifting member 142. The mask is then placed on the upper surface 32 of the adjacent workpiece and aligned relative to the workpiece so that the area excluded from exposure is covered by the mask. Whether the mask 70 is in contact with the upper surface 32 of the workpiece depends on the size of the main body 72 and / or the ball 202.

  As described above, the alignment of the mask 70 may be performed by engaging one or more balls 202 fixed to the mask with the restraining member 204 fixed to the workpiece stage (FIG. 6). For example, as shown in FIG. 7, if the mask 70 is a ring mask and the desired exposure exclusion region 210 is the annular adjacent end 34 of the workpiece, the mask edge 76 is the end of the workpiece 30. A mask is placed and positioned to cover a portion of workpiece surface 32 near 34.

  As shown in FIG. 3, when the mask 70 is positioned, the workpiece stage 16 is returned to the exposure position under the projection lens 14. At this time, alignment and focusing of the workpiece for exposure are performed. If the mask 70 is attached to the workpiece and interferes with the focus system and / or alignment system (not shown) of the lithography tool 10, these processes may need to be modified appropriately. Also, the main controller 44 may need to recognize the presence or absence of the mask 70 so that the operation of the lithography tool 10 can be changed to accommodate the mask.

  When the masked workpiece 30 is placed in place under the projection lens 14, the masked workpiece is exposed one or more times by lithography to form one or more exposure fields 36 (FIG. 2). . This exposure process may include, for example, formation of bump wiring for bump lithography. When the masked workpiece is exposed, the workpiece stage 16 moves to the workpiece mounting position. The control unit 200 operates the mask handling device 60 so that the mask lifting member 142 can engage with the mask 70 and lift the mask 70 from the workpiece 30.

  As shown in FIG. 8, when the workpiece 30 is masked with the ring mask 70, a portion 218 (broken line portion) corresponding to the exposure exclusion region 210 of the negative photoresist layer 40 is removed from the workpiece during processing (for example, development). Is done. For this reason, direct electrical contact with the workpiece upper surface 32 is obtained at or near the end 34. As described above, such contact is required in photolithography such as bump lithography.

  When the mask 70 is removed by the mask handling device 60, the first workpiece can be removed from the workpiece stage 16, and a new (second) workpiece is transferred to the workpiece stage for masking and lithography processes. .

  Many features and advantages of the present invention will be apparent from the detailed description, and therefore, all features and advantages relating to the apparatus described in accordance with the spirit and scope of the present invention will be covered by the appended claims. Further, since various modifications and changes will be readily conceived by those skilled in the art, the present invention should not be limited only to the configurations and embodiments described in this specification. Accordingly, other embodiments are intended to be within the scope of the claims.

1 is a schematic view of a lithography tool that includes a mask of the present invention positioned relative to a workpiece. FIG. It is a top view of the workpiece which shows the exposure area | region formed in the photosensitive surface of a workpiece. FIG. 2 is a perspective view showing the workpiece stage of the lithography tool shown in FIG. 1 together with an example of an operatively connected mask handling apparatus, and that the workpiece stage is at a workpiece mounting position relative to the projection lens. Show. It is a perspective view of a ring mask suitable for a circular and flat workpiece such as a normal semiconductor wafer. FIG. 5 is an enlarged cross-sectional view of the ring mask of FIG. 4 coated with a photoresist layer and positioned relative to a workpiece located on a workpiece stage. FIG. 6 is an enlarged perspective view of the ring mask arranged as shown in FIG. 5 as viewed from above, showing a state where a restraining member on the surface of the workpiece stage is engaged with one of the balls of the ring mask. FIG. 6 is a cross-sectional view of the ring mask shown in FIG. 5 positioned proximate to the photoresist layer of the workpiece to form a ring-type exposure exclusion region proximate to the end of the workpiece. FIG. 8 is a cross-sectional view similar to FIG. 7 after the workpiece has been processed, showing a state in which a portion corresponding to the ring-type exposure exclusion region of the photoresist layer has been removed.

Claims (16)

A method of forming an exposure exclusion region in a selected region of a photosensitive workpiece, comprising:
A step (a) of mounting the workpiece on a movable workpiece stage at a mounting position;
(B) after the step (a), placing a mask on the workpiece and completely covering the selected area;
(C) after the step (b), moving the workpiece stage from the mounting position to an exposure position where a part of the lithography tool including the projection lens is disposed above;
After the step (c), the workpiece and the mask are exposed by radiation from the exposure apparatus without exposing the selected area covered by the mask, and are covered with the mask on the workpiece. A step (d) of drawing a micro-shape on a non-surface,
A step (e) of moving the workpiece stage from the exposure position to the mounting position after the step (d);
(F) removing the mask on the workpiece stage after the step (e);
Including
The mask is an opaque member that does not transmit the wavelength of the radiation that activates the photosensitive workpiece;
A method in which the selected area of the workpiece that has not been exposed is set as an exposure exclusion area . In claim 1,
The mask has a ring shape, and wherein In the step (b), the are arranged in contact close to the surface of the workpiece, the method. In claim 1,
The method in which the step (b) of disposing the mask and the step (f) of removing the mask are each performed by a mask handling apparatus having a vacuum contact. In claim 1,
The mask is conductive;
Before the step (a), including the step (g) of arranging the mask at the mounting position,
The step (f) and the step (g) are performed by a mask handling apparatus having a magnetic contact. In claim 1,
The method of drawing the micro shape in the step (d) is performed by a lithography exposure apparatus . In claim 1,
Before the step (a), coating the workpiece with a negative photoresist to form the photosensitive workpiece (h);
(I) performing a process of removing the negative photoresist from the selected region after the step (f);
Including a method. In claim 1,
A method comprising the step (j) of moving the workpiece stage to the mounting position before the step (a) . In claim 1,
The workpiece stage has at least one restraining member,
In the step (b) of arranging the mask, the step (k) of engaging the restraint member and the mask in order to fix the mask at a position relatively aligned with the surface of the workpiece. Including a method. An apparatus for forming an exposure exclusion region in a selected region of a photosensitive workpiece,
A workpiece stage movable between a mounting position and an exposure position;
A mask that does not transmit wavelengths of radiation that activate the photosensitive workpiece;
An illumination projection device that is part of a lithography tool that irradiates the workpiece and the mask with the radiation and draws a micro-shape when the workpiece stage is in the exposure position;
Including
The workpiece is mounted on the workpiece stage at the mounting position;
The workpiece stage holds the workpiece at the mounting position,
The mask is disposed on the workpiece stage in the mounting position, in proximity to the surface of the workpiece, covers the selection area, and is further held on the stage,
The selected area excluded from exposure by the mask is the exposure excluded area;
The mounting position is separated from the exposure position . In claim 9 ,
The apparatus, wherein the mask is a ring configured to cover the selected area, which is an annular area of the workpiece. In claim 10 ,
The apparatus includes an annulus having an inwardly projecting edge. In claim 9 ,
An apparatus comprising: a mask handling device configured to engage the mask with the workpiece and remove the mask from the workpiece in the loading position . In claim 12 ,
The apparatus, wherein the mask is made of a conductive material . In claim 10 ,
It said ring-like region of the workpiece has a width of 1 to 5 mm, device. In claim 10 ,
The device, wherein the ring has a radius of 50-150 mm. In claim 11 ,
The device, wherein the edge has a thickness of 0.1 to 0.4 mm.

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